UPDATE 1-U.S. natgas futures fall to 14-year low on weak heating demand

(Adds latest prices) Dec 15 (Reuters) - U.S. natural gas futures fell nearly 3.8 percent to a 14-year low on Tuesday on forecasts for continued unseasonably mild weather that is expected to curb heating demand through late December. Front-month gas futures on the New York Mercantile Exchange declined for a fifth straight trading day, closing down 7.2 cents, or 3.8 percent, at $1.822 per million British thermal units. The January future fell to a contract low of $1.797 after the settle